This proposal describes on-going research programs in biochemistry, microbiology, pharmacology are molecular biology currently funded by the NIH, which require mass spectrometry support. This proposal requests funds to purchase a MALDI mass spectrometer and data system capable of analyzing biopolymers with molecular eights as high as 100,000 and sample sizes in the picomole or less range. The instrument also can provide MS/MS-type data through the PSD experiment. This instrument will be house in the MSU Mass Spectrometry Facility, in the Biochemistry Building. In this Facility, the P.I. is a Core- Director. Professor J.T. Watson is currently the Director, and Professor Douglas Gage is Co-Director and Manger of this Facility. The instrument is requested to support the research projects of nine research groups, at MSU and in the Mid-Michigan area. Types of mass spectrometric studies include: peptide mass mapping to identify proteins of biological interest; identification of sites of post-translational modification, particularly sites of phosphorylation, but also including nitrosylation, ubiquitination, polyhydrioxybutyrate adduction and disulfide bond location; and mapping of protein-ligand binding sites using bifunctional cross-linking reagents. These studies cannot otherwise by aggressively pursued due to limitations in the Facility's current instrumentation. The MSU Mass Spectroscopy Facility continues to receive strong support from the University and the College of Natural Science. This state-of- the-art MALDI instrument will provide an important complement to the existing mass spectroscopic instrumentation located in the Facility, and will impact a substantial number of researchers across various disciplines of biomedical research.